The mighty Southeastern Conference's aura of invincibility has taken a hit just a couple weeks into this season.

Sure, the SEC has half its members ranked in the Top 25 this week, and the conference keeps grabbing big headlines with its schools playing the country's must-see games every week. No. 1 Alabama and sixth-ranked Texas A&M are next up Saturday.

But the SEC's dominance in nonconference play has slipped.

The league of champions already has lost four nonconference games — half as many losses as the SEC lost all of 2012. The SEC has lost to the Atlantic Coast Conference, the Big 12 and even the Sun Belt. This week, the American Athletic Conference and Pac-12 are lining up to take a shot at college football's power conference.

Not that anyone has panicking.

"The SEC's still the SEC," Tennessee quarterback Justin Worley said. "We've got some great teams in our conference. I think Clemson was a great team that beat Georgia and Miami's kind of a team on the rise, I think, right now. I wouldn't say it's surprising because there are still good teams out there throughout the nation."

Still, everyone is looking for any glimpse of vulnerability hoping to end the SEC's stranglehold on the national title.

The SEC is 19-4 through two weeks in nonconference play after going 48-8 in 2012, not counting bowls. The ACC has earned two big wins against the SEC. Clemson beat Georgia 38-35 in the big game of this season's opening week, while Miami upset Florida 21-16 last week.

Clemson coach Dabo Swinney said those were big games for the ACC.

"People ask you about the ACC over the past few years, and my answer's always been, 'Listen, you've got to win games.' It's that simple," Swinney said. "There's nothing anybody can do about anything until you win games. So it's good to see teams take advantage of an opportunity."

No. 7 Louisville, joining the ACC next July, should beat Kentucky on Saturday and give the American Athletic Conference a rare SEC pelt. Swinney's team will have a chance to bookend SEC victories for the ACC when Clemson wraps up at South Carolina.

Georgia bounced back from that loss to Clemson by beating South Carolina, which opened the season thumping North Carolina 27-10.

Mississippi coach Dan Mullen's Bulldogs lost their opener 21-3 to Oklahoma State on a neutral field in Houston.

"That's what makes the SEC the SEC. You have to be ready to go week in and week out," Mullen said.

Mullen said just look at the schedules these teams from other leagues play. The SEC team usually is everyone's big game of the season, though some might have another big game or two allowing plenty of rest against cupcakes the rest of the year.

"In the SEC, you end up with about eight tests a year because every single game you've got to be on your A game or you can get beat," Mullen said. "That's just what makes the league so tough."

Tennessee knows that firsthand.

The Volunteers put a 12-game nonconference winning streak in the regular season on the line Saturday when they visit No. 2 Oregon, the last team outside the SEC to beat Tennessee back in 2010. The Pac-12 perennial power is just the first of five ranked opponents the Vols will play in the next six games. The other four ranked foes during that stretch are all SEC teams: Florida, Georgia, South Carolina and Alabama.

No. 25 Mississippi visits Texas on Saturday in another game that could dent the SEC's nonconference superiority. The Rebels get a week off before visiting Alabama.

It's the kind of schedule that forces teams in the SEC to improve just to survive. Or else.

Western Kentucky, a Sun Belt team moving to Conference USA next July, got an up-close look at how challenging SEC play can be. The Hilltoppers knocked off Kentucky to open the season, but coach Bobby Petrino couldn't go 2-0 as Tennessee routed Western Kentucky 52-20 for a little SEC payback.

Still, bouncing back is what matters most in the SEC where not even a loss kept Alabama from playing for and winning its third national title in four years. How Georgia rebounded from its loss to Clemson certainly impressed CBS analyst Gary Danielson.

"I believe that right now Georgia is the team to beat in the East," Danielson said.

And winning the SEC East usually puts a team a win away from playing for a national championship.

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AP Sports Writers Pete Iacobelli in South Carolina, Steve Megargee in Knoxville, Tenn., David Brandt in Mississippi and John Zenor in Alabama contributed to this report.